In International PCT patent application publication WO2009/153764 published on 23 Dec. 2009 and commonly owned by the present applicant, there is described a tunable liquid crystal optical device, such as a lens, that has a liquid crystal electrical control field electrode that uses a weakly conductive or highly resistive material in combination with the electrode and cell geometry that allows for tuning of the optical property of the device using a frequency of the control signal. For example, a hole patterned electrode can be used on one side of the liquid crystal cell, while a planar electrode can be used on an opposed side of the liquid crystal cell. A layer of the highly resistive material or highly resistive layer (HRL) can be provided near the hole patterned electrode.
In the absence of the HRL, the electric field would be concentrated at the periphery of the lens aperture due to the geometry, for example, a lens aperture can be about 3 mm with a cell thickness of about 50 microns. With the spacing between the electrodes about 60 times smaller than the diameter, it will be understood that the electric field cannot spread out to control the central part of the lens. Also, the electric field lines are not parallel to the optical axis of such a lens, and thus asymmetry about the optical axis of the liquid crystal arises. The inclusion of such an HRL is to cause the electric field at the hole patterned electrode to appear across the entire aperture with a gradual decay in strength from the periphery to the center optical axis. The electric field lines are also essentially parallel to the optical axis.